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FERGUSON, MO (KTVI) – Shots rang out late Sunday night after a peaceful march in Ferguson to mark the death of Michael Brown.

The St. Louis County Police Department tweeted the following information on Sunday night shooting in Ferguson: “The St. Louis County Police Department was involved in an officer-involved shooting after officers came under heavy gunfire.”

The shooting occurred around 11:10 p.m. in the 9200 block of West Florissant, from a section on the street north of the police and protesters’ position near the Ferguson Market.

The gunfire caught police and protesters off guard. Demonstrators and officers ducked as the shots rang out. About 250 people were on West Florissant Street after the march at around 9:30 p.m. The crowd thinned considerably hours after the shooting.

Family members tell Fox 2 the person wounded in the police shooting is 18-year-old Tyrone Harris Jr. Harris is listed in critical and unstable condition.

Police said two people exchanged gunfire from across West Florissant. Officers in an unmarked vehicle drove toward one of those individuals, identified as Harris. Harris then allegedly opened fire on officers in that unmarked vehicle. The officers got out of the vehicle and chased Harris on foot behind a business in the 9200 block of West Florissant. Harris attempted to fire at the officers again, but was shot.

A 9mm handgun was recovered at the scene. It had previously been reported stolen out of Cape Girardeau.

Harris’ family said he was a friend and classmate of Michael Brown. The family said Harris was with his girlfriend and other friends on West Florissant. His father said Harris had just graduated from Normandy High School and was planning to attend a technical college in the fall.

The family was not allowed inside the hospital to see Harris. No reason was given as to why, however, hospital officials said county police were handling family requests to see Harris.

Two other incidents occurred during the protest on West Florissant: one was a young woman who suffered a seizure during the shots fired and another person was injured by flying glass at the scene.

Three county police officers suffered minor injuries during Sunday night’s events. Two officers were hit with pepper spray and a third was struck in the face by a rock.

Four people were arrested in all, county police said.

Missouri Governor Jay Nixon released the following statement Monday afternoon:

“Last night, after a day of peaceful marches, prayers and healing, a number of violent incidents occurred: law enforcement officers were fired upon, businesses were burglarized, a reporter was attacked, a drive-by shooting took place, and the entire community was put at risk by heavy gunfire exchanged among groups of armed criminals. This is a sad turn of events, and I thank the brave and dedicated law enforcement officers who worked into the early morning hours to protect citizens, businesses as well as peaceful protesters and members of the media. Those who terrorize communities with gunfire and commit violence against police officers are criminals, and their reprehensible acts must not be allowed to silence the voices of peace and progress. Over the last year, people of good will across the community have worked tirelessly to bridge divisions, restore trust and build a brighter, safer, and more united future for the region. For the sake of all, it is my hope and expectation that today’s events will be peaceful so that these efforts can continue to move the region in a positive direction.”

More details will be posted as this story develops.